Pervaporation (PV) using zeolite membrane is one of the emerging technologies undergoing a rapid growth in recent years, regarded as an alternative method to distillation for its energy-efficient. However, grain boundary defects, especially for hydrophilic zeolite membranes, inevitably formed due to their polycrystalline structures and strong negative surface charges of Al-containing zeolites during hydrothermal synthesis, degrade their selectivity by providing nonselective transport pathway for permeating species. We show that functional defect-patching (FDP) can improve the PV performances of thin columnar membrane of a certain zeolite (mordenite) by eliminating grain boundary defects, by grafting functional polymer groups onto grain boundaries. This methodology enables the preparation of mordenite zeolite membrane (MZM) with high PV performances for the dehydration of acetic acid (AcOH) and holds promise for realizing high-throughput and scalable production of the membrane with improved energy efficiency. Furthermore, durable tests for acid stability showed that the FDP-treated membrane displayed a reasonably strong acid resistance. Finally, the products fabricated were characterized by a variety of techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), diffuse reflectance FT-IR spectroscopy (DRIFTS) and thermogravimetric analysis (TGA).Graphical abstractResearch highlights▶ FDP is an effective means for elimination of the grain boundary defects. ▶ FDP markedly improves the PV performances of the MZM. ▶ The membrane P4VP-2 is moderately more productive than the membrane PVI-2. ▶ Acid stability of the FDP-treated membrane by P4VP groups improves greatly. ▶ The functional groups effectively prevented dealumination from zeolitic surface.

A novel hydrophilic poly(1-vinylimidazole)/mordenite (PVI/MOR) grafting membrane was prepared by free-radical graft polymerization of 1-vinylimidazole (VI) onto the as-synthesized mordenite zeolite membrane. The surface property and the morphology of the membranes were analyzed by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), diffuse reflectance FT-IR spectroscopy (DRIFTS) and thermogravimetric analysis (TGA). The effects of VI concentrations in the grafting medium, separation temperature, feed concentration on selectivity and flux of the obtained membranes for pervaporation dehydration of acetic acid were examined.The PVI/MOR grafting membrane with the VI solution of 15 wt.% astonishingly exhibited the ideal selectivity with water contents in permeates reaching 100.00 wt.% over acetic acid feed concentrations from 71 to 94 wt.% at 80 °C. Both the total fluxes and selectivity for this membrane increased with temperature ranging from 40 to 80 °C. It was suggested that an in situ formed complex between the poly(1-vinylimidazole) (PVI) moiety of the membrane and the acetic acid in the feed played an important role in the separation performance. It not only blocked the permeation of acetic acid through the grain boundary defects but also facilitated the transport of the water molecules, resulting in an ideal selectivity of water over acetic acid.